30 ! 1) сколько требуется меди на провод длиной 10 км, сопротивление которого должно быть 10 ом? плотность меди р=8.5 г/см^3. 2) никелиновая спираль электроплитки имеет длину 5 м и площадь поперечного сечения 0, 1 мм^2. плитку включают в сеть с напряжением 220 в. какой силы ток будет в спирали в момент включения электроплитки? 3)каково напряжение на концах железной проволоки длиной 12 см и площадью поперечного сечения 0, 04 мм^2, если сила тока, текущего через эту проволоку, равна 240 ма?

1)
L=10 км=1 10⁴ м                  масса провода:  m=dV=dLs;
R=10 Ом                            d-плотность; L-длина; s-площадь сечения;
d=8,5 г/см³=8,5 10³ кг/м³  s-найдем из ф-лы сопротивления;
ρ=1,8 10⁻⁸ Ом м               R=ρL/s;  s=ρL/R;
m-?                                    s=1,8 10⁻⁸1 10⁴/10=1,8 10⁻⁵ м²
                                         m=8,5 10³*1 10⁴1,8 10⁻⁵=15,3 10² кг=1530 кг
                                                                    ответ: m=1530 кг.

I live in a house. I really like my house. It's small, but I'm not small either. When you enter the house, you can see a small kitchen. In the kitchen, we cook and eat. I spend a lot of time in the kitchen Because I like to eat.  the next room is the hallway. in the hallway there is a large closet on the entire wall. there are no Windows. we go through the hall to the other rooms. our hall is very large. there is a large sofa. the hall is very bright because there are many Windows. there are many different colors in the hall. my parents ' and sister's room is very large. They have one room. There is a large TV hanging there, it is located above the bed and there is a bedside table to the right of the bed. In the second half of the room is my sister's sofa. my room is the smallest. I even like it. my room has a pull-out sofa, a table, and a TV. there is a courtyard around the house. "My mother likes to grow flowers. we have a sauna in our yard. and we also have a dog that lives in a booth that dad built. We have a garage for my father's car and tools. We also store our things there.

Привет очень сложно бяло моему перекладачу но справился )))хахаха

I live at home. I really like my house. it is small, but I am not small either. When you enter the house, you see a small kitchen. in the kitchen we cook and eat. I spend a lot of time in the kitchen, because I like to eat. The next room is the entrance hall. in the hallway there is a large closet over the entire wall. there are no windows. through the hallway we go into other rooms. our room is very large. there is a large sofa. the hall is very bright because there are many windows. there are many different colors in the room. The room of my parents and sister is also large. a large TV hangs to the room, it hangs above a large soft bed and there is a bedside table to the right of the bed. and in the second half of the room is my sister’s sofa. my room is the smallest. I even like it. To my room there is an extendable sofa, a table and a TV. there is a yard around the house. My mother loves to grow flowers. we have a bathhouse in our yard. and we also have a dog that lives in a booth that dad built. We have a garage for my father’s car and tools. We also store our things there.